1. Field of the Invention
The present invention relates to an image forming apparatus such as a digital copying machine, a computer printer and a network printer, and an image processor which is the image processing section of the above image forming apparatus.
2. Description of the Related Art
In many image forming apparatuses such as a digital copying machine, a computer printer and a network printer which are on the market, an electrophotographic method which enables obtaining a high quality of image at a high speed is widely adopted as an image output device.
In the electrophotographic method, an electrostatic latent image on a photoconductive drum is developed by electrifying insulated toner by mixing insulated toner and a magnetic particle in a developing machine, forming a developer on a developing roller by magnetic force in the shape of a brush and supplying the developer onto the photoconductive drum by rotating the developing roller as developing means. A two-component system magnetic brush developing method is widely used and particularly, in a color image forming apparatus, it is more widely adopted. An electrostatic latent image on a photoconductive drum is formed as the strength of electrification potential according to the signal strength of a picture signal by scanning, modulating a laser beam for example according to a picture signal after evenly electrifying an electrostatic latent image on a photoconductive drum.
However, depending upon the strength of electrification potential on a photoconductive drum, toner may behave differently from an aim because of various reasons, an image to be developed is not developed and a so-called void may occur.